This invention relates to a cationic electrodeposition negative type resist composition having high sensitivity and high resolution and hence suited for the preparation of, for example, a printed circuit board having a fine circuit pattern.
A dry film has hitherto been used extensively as an etching resist adapted for the preparation of a printed circuit board. However, since the dry film has an increased film thickness, it is poor in resolution, and the wiring pattern can not be made fine beyond a certain limit, such that the dry film can not successfully cope with refinement of the wiring pattern required for high density mounting of wiring devices in a wiring circuit board for a printed circuit employed in recent electrical and electronic equipments.
Thus, a technique of preparing a fine wiring pattern by an etching resist has been developed. The etching resist makes use of an electrodeposition coating method whereby a thin film can be coated uniformly. The electrodeposition etching resist is classified into an anionic type and a cationic type. Since an acidic solution is used for copper etching, the anionic type resist, which gives a coating film exhibiting acid resistance after curing, has been a main subject of studies and investigations.
However, the anionic electrodeposition etching resist has a drawback that, since an electrical voltage is applied during electrodeposition coating with the coated material as an anode, metal is eluated to react with carboxylic acid in the resin precipitated by electrodeposition to form salts which are difficultly soluble in an alkaline developing solution and which are mainly responsible for lowered developing properties. The anionic resist also has a drawback that, if the impressed voltage is lowered to reduce the amount of metal eluation, uniform spreadability, which is among the characteristics of the electrodeposition coating process, is lowered, so that a uniform thin film cannot be produced.
On the other hand, the cationic electrodeposition etching resist has a drawback that, although it is not subject to metal eluation because the electrical voltage is applied with the coated material as the cathode, the etching resist film before cured exhibits high tack and hence a photomask cannot be brought into tight contact therewith such that resolution as well as acid resistance of the film is markedly lowered during exposure or the coating film cannot be cured sufficiently.